Economic Optimization in the Non-Steady-State Periodic Orbit under Zone Model Predictive Control for the Chemical Process: A Case Study of a Heavy-Oil Fractionator

Abstract

This study designs a new control strategy which uses a non-steady-state optimization strategy in zone target control systems. This paper first analyzes the limitations of the classic steady-state optimization strategy. Through the spatial position relationship between the open-loop steady state feasible range and the zone control target, the barriers restricting the improvement of economic optimization performance are explained. Second, this paper introduces a switching control strategy which can be used for the zone control system, and this control strategy divides the state space of the system into two independent spaces for separate design. When the state variable of the system is detected and if it does not belong to the zone target, the value of the input variable of the system will be calculated by the zone model predictive controller to ensure that the state can be driven into the target. When the state of the system is detected inside the zone target, it can always remain in the optimization mode by this strategy. We adopt a tracking model predictive control strategy so that the system can keep track of this periodic orbit. The effectiveness of the optimization strategy proposed in this paper is verified by the numerical simulation, and the results show that the periodic orbit optimization strategy can improve comprehensive economic indicators.